【作者】 孙杰；

【导师】 吴磊； 王建；

【作者基本信息】 电子科技大学 ， 软件工程， 2014， 硕士

【摘要】 Internet是一个巨大的资源网和通信网,它是由千千万万个称为自治系统(简称AS)的路由域构成。其中每个自治系统分别从属于不同的网络服务提供商。系统内部路由器之间通过内部网关协议来交换路由信息,自治系统之间路由器之间则是通过外部网关协议来交换路由信息和进行路由选择,边界网关协议BGP是目前运行于Internet上的事实上的外部网关协议。BGP协议是根据自治系统所制定的路由策略来选择抵达目的网络的最佳路由,由于各方面利益的原因,每个自治系统都独立制定自身的路由策略,这样所制定出的路由策略往往存在冲突。研究表明路由策略冲突会导致BGP路由振荡的发生。所谓BGP路由振荡就是指多个自治系统之间不断交换BGP路由信息,使得BGP路由不能收敛于稳定的路由。BGP路由不稳定会影响整个网络的性能。本文首先分析了实例中路由选择过程,阐明了路由振荡现象,根据路由振荡现象,详细的分析产生振荡的原因。其次,对BGP路由的震荡的抑制过程出现的相关的问题进行了研究,并提出了方案的分析和方法,来解决研究在实际网络中使用它的范围,找出当前解决BGP快速的收敛中遇到的问题,便于下一步优化。在对边界网关路由振荡进行分析之后,提出了对于解决BGP路由振荡的方案,进而解决BGP路由策略冲突所造成的路由振荡问题。通过Griffin T G提出简单路径向量协议,对在路由策略发生冲突的情况下所产生的最佳路由作上标记,表明该路由与策略的冲突有关,在后续的路由选择中如果该路由要是再次被标记,就表明路由策略冲突导致的路由振荡发生。当路由策略导致路由振荡发生时,不再选择被标记的路由,而是选择具有较短AS路径的路由,这样就可以消除路由振荡。为了检测路由策略冲突,消除路由振荡,对BGP协议进行了修改使之携带与策略冲突检测相关的信息。运用网络仿真工具SSFNET对改进后的路由协议进行测试,证实了所给方法的有效性。更多还原

【Abstract】 Internet is a large communication and resources network that is composed of thousands of autonomous systems(AS), called routing domain. These autonomous systems belong to different network service providers respectively. Routers inside the autonomous system exchange routing information through interior gateway protocol. Routers belonging to different autonomous system exchange routing information and select routes through exterior gateway protocol. The border gateway protocol(BGP) is the de fact exterior gateway protocol running in the Internet. The border gateway protocol selects the best routes to destination network according to the routing policies developed by the autonomous system itself. Due to the business interests, every autonomous system develops routing policies independently. The routing policies belonging to different autonomous systems usually exists conflicts. Study shows that the routing policy conflictions between AS can cause BGP routing oscillation. The so called BGP routing oscillation is refer to the fact that routing information is exchanged continually among different AS. These autonomous systems can not have a stable route. BGP routing instability can affect the function of the Internet.In this paper, we firstly analyze the routing selection process in instance, and illustrate the route oscillation phenomenon. According to the route oscillation phenomenon, the cause of oscillation is analyzed in detail. Secondly, the problems related to the BGP route flapping inhibition appeared are studied and the analytical and methodological solutions are proposed in order to address the scope of research to use it in real networks. Moreover, the current resolve BGP fast convergence in case of to the problem is found out so as to allow the next optimization. After the analysis of border gateway routing oscillations, the route oscillation problem solving oscillations of BGP routing scheme is proposed which solves the BGP routing policy conflicts caused.Based on the simple path vector protocol proposed by Griffin T. G. a method to eliminate the route oscillation is given. In this method, the best route is marked when routing policy conflict is detected. When the same route is marked once again in the follow up route selection, it is demonstrated that there is a route oscillation caused by policy conflict. When route oscillation caused by policy conflict is detected, the marked route is no longer selected as the best route, and another route with short AS path is selected. Thus the route oscillation can be eliminated. In order to detect policy conflict and eliminate route oscillation, the BGP protocol is modify to carry information relation to policy conflict. The modified BGP is tested using network simulation software SSFNet. Simulation results confirm the validity of the method.更多还原